The need for door security has increased significantly, especially in high density population areas where condominiums, office buildings, apartments, hotels, etc., are located. Outside doors are especially susceptible to break-in and unauthorized entry where the latch bolt may be exposed between the end face of the door and the doorjamb and may be unlatched with a simple or readily available tool or even a thin, flexible plastic card, or the like to gain entry from the outside, or hallway or corridor. Although a number of systems have been proposed heretofore, including those disclosed in U.S. Pat. Nos. 2,144,075, 1,399,897, 3,606,429, 3,290,081, 3,764,173, 4,180,568, 4,390,199, 4,484,463, and 4,547,009, none have been entirely suitable or widely accepted. It is to an improved door security system which may be easily installed that the present invention is directed.